safety switch
 保險開關; 安全開關


 Safety chain. (a) Railroads A normally slack chain for preventing excessive movement between a truck and a car body in sluing. (b) An auxiliary watch chain, secured to the clothes, usually out of sight, to prevent stealing of the watch. (c) A chain of sheet metal links with an elongated hole through each broad end, made up by doubling the first link on itself, slipping the next link through and doubling, and so on.
 Safety arch Arch., a discharging arch. See under Discharge, v. t.
 Safety belt, a belt made of some buoyant material, or which is capable of being inflated, so as to enable a person to float in water; a life preserver.
 Safety buoy, a buoy to enable a person to float in water; a safety belt.
 Safety cage Mach., a cage for an elevator or mine lift, having appliances to prevent it from dropping if the lifting rope should break.
 Safety lamp. Mining See under Lamp.
 Safety match, a match which can be ignited only on a surface specially prepared for the purpose.
 Safety pin, a pin made in the form of a clasp, with a guard covering its point so that it will not prick the wearer.
 Safety plug. See Fusible plug, under Fusible.
 Safety switch. See Switch.
 Safety touchdown Football, the act or result of a player's touching to the ground behind his own goal line a ball which received its last impulse from a man on his own side; -- distinguished from touchback. See Touchdown.  Same as safety
 Safety tube Chem., a tube to prevent explosion, or to control delivery of gases by an automatic valvular connection with the outer air; especially, a bent funnel tube with bulbs for adding those reagents which produce unpleasant fumes or violent effervescence.
 Safety valve, a valve which is held shut by a spring or weight and opens automatically to permit the escape of steam, or confined gas, water, etc., from a boiler, or other vessel, when the pressure becomes too great for safety; also, sometimes, a similar valve opening inward to admit air to a vessel in which the pressure is less than that of the atmosphere, to prevent collapse.

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 Switch n.
 1. A small, flexible twig or rod.
    Mauritania, on the fifth medal, leads a horse with something like a thread; in her other hand she holds a switch.   --Addison.
 2. Railways A movable part of a rail; or of opposite rails, for transferring cars from one track to another.
 3. A separate mass or trees of hair, or of some substance (at jute) made to resemble hair, worn on the head by women.
 4. Elec. A device for shifting an electric current to another circuit, or for making and breaking a circuit.
 Safety switch Railways, a form of switch contrived to prevent or lessen the danger of derailment of trains.
 Switch back Railways, an arrangement of tracks whereby elevations otherwise insurmountable are passed. The track ascends by a series of zigzags, the engine running alternately forward and back, until the summit is reached.
 Switch board Elec., a collection of switches in one piece of apparatus, so arranged that a number of circuits may be connected or combined in any desired manner.
 Switch grass. Bot. See under Grass.